1. Field of the Invention
The present invention relates to a display apparatus and a method for driving the same, and more particularly to a display apparatus, such as a plasma display panel (PDP), that repeatedly carries out sustain discharges having sustain discharge pulses (light emission pulses) and adjusts the emission of light based on the number of repetitions, and a method for driving such a display apparatus.
2. Description of the Related Art
With the recent trend toward larger-screen displays, the need for thin display apparatuses has been increasing, and various types of thin display apparatus have been commercially implemented. Examples include matrix panels that display images by directly using digital signals, such as PDPs and other gas discharge display panels, digital micromirror devices (DMDs), EL display devices, fluorescent display tubes, and liquid crystal display devices. Among such thin display devices, gas discharge display panels are considered to be the most promising candidate for large-area, direct-view HDTV (high-definition television) display devices, because of the simple production process which facilitates fabrication of larger-area displays, a self-luminescent property which ensures good display quality, and a high response speed.
For example, in the PDP, one field is divided into a plurality of light emission blocks (subfields: SFs) each comprising a plurality of sustain discharge pulses, and a grayscale is displayed by combining these subfields. That is, the PDP achieves a grayscale display by repeating sustain discharges with sustain discharge pulses and thereby adjusting the light emission time.
During the sustain discharge period, the current (sustain discharge current) is initially small, but gradually increases toward the end of the sustain discharge period as the sustain discharge is repeated. Since power is consumed by the sustain discharge, the sustain discharge voltage decreases in a manner that is inversely proportional to the current, and this decrease of the sustain discharge voltage results in an incomplete sustain discharge; accordingly, there is a need for a display apparatus that can perform control considering the sustain voltage drop when displaying an image that consumes much power, and also a need for a method for driving such a display apparatus.
In this specification, the term “field” is used by assuming the case of interlaced scanning in which one image frame is made up of two fields, an odd field and an even field, but in the case of progressive scanning in which one image frame is made up of one field, the term “field” can be used interchangeably with “frame”.
In the prior art, sustain discharge pulses are set, for example, by calculating a display load ratio for each frame from display data and by performing computation based on the display load ratio for each frame (field) so that the power consumption of the display apparatus will not exceed a predetermined value. Such techniques are disclosed, for example, in Japanese Unexamined Patent Publication (Kokai) Nos. 06-332397 and 2000-098970.
More specifically, Japanese Unexamined Patent Publication (Kokai) No. 06-332397 discloses a flat panel display apparatus comprising an integrating means for integrating the number of pixel signals of a prescribed level applied during a prescribed period, and a frequency changing means for changing the panel driving frequency based on the result of the integration of the integrating means, while Japanese Unexamined Patent Publication (Kokai) No. 2000-098970 discloses a plasma display apparatus comprising an integrating means for integrating, for each bit signal used to achieve grayscale display, the number of pixel signals applied during a prescribed period, and a frequency changing means for changing the frequency of a sustain discharge waveform, based on the result of the integration of the integrating means.
The prior art and its associated problems will be described in detail later with reference to accompanying drawings.